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Top Benefits of Flaxseed

Analysis by Dr. Joseph Mercola Fact Checked

flaxseed health benefits

Story at-a-glance -

  • Animal research shows people who eat a high-fat diet with flaxseed have more beneficial bacteria in their gut and better glucose control than those eating just high fat (without flaxseed) or a standard diet
  • While flaxseed oil has similar benefits, the oil is not rich in fiber and I recommend using whole flaxseed as the oil is delicate and easily oxidized. If you like to use flaxseed oil, add it to salads and soups but only at the end of the cooking process
  • Flaxseed is the richest known source of plant lignans, which can protect against Type 2 diabetes, help maintain bone density and block the effects of estrogen associated with certain cancers
  • The flax plant is highly adaptable and may be grown in most of the U.S. Whole flaxseed may be stored for up to 12 months in an airtight container and ground in a small coffee bean grinder just prior to use, as the ground product is highly perishable and turns rancid rapidly

The flax plant (Linum usitatissimum) has a long and illustrious history spanning nearly 10,000 years. Remains of flax seeds have been found in Stone Age dwellings in Switzerland and Egypt. The plant reached the U.S. in the 1800s with European settlers and is now grown as a nutritional seed harvest and for fiber used in the making of linen.

Although used historically for centuries, it wasn't commonly found on many shopping lists 10 years ago. Flaxseeds contain more polyphenols than vegetables like olives1 and lower your risk of serious diseases such as Type 2 diabetes,2 heart disease and cancer. They are available in a brown or yellow variety and are sold either whole, ground or as flaxseed oil.

The oil should not be confused with linseed oil, which, while made from flaxseed, is reserved for industrial purposes. Although most of the benefits found in flaxseed are also found in the oil, I recommend using whole flaxseed, since flaxseed oil is delicate and easily oxidized. If you like to use flaxseed oil, add it to salads and soups, but only at the end of the cooking process.

Animal research has demonstrated the addition of flaxseed to a high-fat diet protected mice against obesity,3 supporting previous research showing lignans in flaxseed were associated with a lower risk of Type 2 diabetes in women.4

Researchers Discover Flaxseed Fiber Feeds Beneficial Bacteria

The health of your gut is key to attaining optimal health. If you've been trying to lose weight but have seen little progress, the challenge may be helped by feeding your beneficial bacteria.5

Past studies have investigated the breakdown of dietary fiber in the gut, noting it produces changes in the digestive system, ultimately reducing the production of fat tissue and improving your immune function. In a recent study published in the American Journal of Physiology, researchers used an animal model to determine the effect flaxseed would have on weight gain. The animals were separated into four groups:6

  • A control group, eating a standard diet containing 4.6 percent soy-based fiber
  • Experimental group 1, eating a high-fat diet containing no fiber
  • Experimental group 2, eating a high-fat diet containing 10 percent indigestible cellulose fiber
  • Experimental group 3, eating a high-fat diet containing 10 percent flaxseed fiber

The team used several measurement factors, including oxygen burned, carbon dioxide produced and energy expended. At the end of the trial, glucose tolerance was also measured. The mice were fed a consistent diet over 12 weeks, after which bacteria and other biological materials were collected from the beginning of the large intestine.

Those eating only a high-fat diet had fewer bacteria associated with improved metabolic health and more bacteria linked to obesity compared to the other three groups. The mice that fared best ate indigestible cellulose or flaxseed, however those eating flaxseed also had better glucose control and higher levels of beneficial fatty acids, compared to the control group.7 According to the researchers:8

"Our data suggest that flaxseed fiber supplementation affects host metabolism by increasing energy expenditure and reducing obesity as well as by improving glucose tolerance. Future research should be directed to understand relative contribution of the different microbes and delineate underlying mechanisms for how flaxseed fibers affect host metabolism."

The Importance of Lignans

These results highlight the importance of lignans in the diet. Lignans are a class of secondary metabolites from plant products demonstrating numerous beneficial biological effects in mammals.

They are found in nuts, seeds and vegetables and drinks such as tea and coffee. Lignans are converted by intestinal bacteria to enterolignans — enterodiol and enterolactone. Also called mammalian lignans, they were discovered independently by two research teams at nearly the same time. 9

These enterolignans perform a variety of biological activities, including anti-inflammatory and apoptotic effects that have an influence on disease. Flaxseed is the richest known source of plant lignans and when diets have been supplemented with flaxseed, it substantially increases the formation of enterolactone in the gut.

In a another study evaluating gut microbiota metabolites of dietary lignans against the risk of Type 2 diabetes, researchers discovered the presence of enterolactone was highly associated with a lower risk of Type 2 diabetes in U.S. women.10

Additional Health Benefits of Flaxseed

As flaxseeds are high in lignans, they play a significant role in blocking the effects estrogen may have in producing estrogen-driven cancers such as breast, uterine, ovarian and prostate cancer.11 Postmenopausal women with high intakes of dietary lignans have a 15 percent lower risk of breast cancer than women with low intake.12

A meta-analysis of 21 studies13 also linked high lignan intake with a reduced risk of breast cancer, while a Canadian study14 found a diet high in flaxseed was associated with a reduction in breast cancer risk. 

Researchers have discovered phytoestrogens'15 effect on the bone can help maintain density and in the case of osteoporosis, suggesting enterolactone excretion is positively associated with bone mineral density in the spine and hips in post-menopausal women.

Flaxseed is one of the best sources of alpha linolenic acid (ALA), a plant-based omega-3 fat.16 ALA may help reduce inflammation in your arteries and reduce tumor growth. One tablespoon contains 3 grams of dietary fiber in soluble and insoluble form.17

Aside from feeding beneficial bacteria in your gut, soluble fiber also helps maintain blood sugar and cholesterol levels, while insoluble fiber helps maintain digestive health by binding to water and helping food pass through your intestines more quickly.

Flaxseed contains a high level of vitamins including E, K, C and several B vitamins. The seed is also rich in calcium, iron, magnesium and phosphorus, essential to maintaining a variety of bodily functions and supporting your overall health.18

Grow Your Own Flaxseed and Store for Maximum Freshness

The flax plant is highly adaptable and can be grown in most of the U.S. The plant enjoys plenty of sun with fertile, well-draining soil. While it appreciates cool weather best, you may be successful by planting in an area where the plant receives afternoon shade.

There are several varieties of flax plants that grow well in different hardiness zones. Discover more tips to grow and harvest at home in my previous article, "How to Grow Flax for Seeds and Fiber."

It's important to keep your flaxseed fresh. If you purchase it already ground, it has a shorter shelf life than the whole variety. Even when carefully packaged, ground flaxseed may only last from six to 16 weeks.

On the other hand, whole flaxseed may last up to 12 months when stored in an airtight container. When sold in bulk at large grocery stores they should be covered and sold on a regular basis to ensure freshness. Flaxseed are highly perishable and turn rancid rapidly.

Buy organic whole seeds and grind them yourself in a small coffee grinder just before use. Your nose can often tell you whether or not your flaxseed has turned rancid. When testing oil or ground seed, inhale deeply to determine if there's a slightly bitter odor similar to old cooking oil. If it tastes strong or burnt, it's likely rancid.

Fermented Foods Add Fiber and Beneficial Bacteria

Adding fermented foods to your daily regimen of flaxseed is yet another way of protecting your gut microbiome. Fermentation has traditionally been used in many cultures around the world in order to enhance foods and prevent spoilage. Regularly eating fermented vegetables is an incredibly powerful way to nourish your gut microbiome and boost your fiber intake.   

While you can purchase high-quality fermented foods from reputable sources, I recommend making them at home since you know they were prepared properly, exactly what's in them and can customize your recipe to include the exact ingredients you enjoy. When using a specific starter culture, your fermented vegetables will also be a rich source of vitamin K2.

The probiotics from fermented vegetables help break down and eliminate toxins from your body, assist in the absorption of minerals and help you maintain your ideal weight. For an easy recipe of how I make fermented vegetables, see my previous article, "How to Make Your Own Fermented Vegetables."

Easily Add Flaxseed to Your Daily Routine

Flaxseed is a powerhouse of nutrition and fiber that can have a significant impact on your gut microbiota and may reduce your risk of Type 2 diabetes. If you don't grow your own flax at home, purchase organic, local, non-GMO certified flaxseed and pay attention to the "use by" date.19

I take one tablespoon of organic brown flax seeds nearly every day.  I used to grind them fresh and add them to my smoothie, but I think a far better way is to soak them overnight and then grind them up.20

If you're just getting started with flaxseed, remember they're rich in fiber so start slow and build up your tolerance, and be sure to drink plenty of water. It's also important to remember there are several side effects21 associated with eating flaxseed.

These may include allergies, hypoglycemia and stool problems. Flaxseed and flaxseed oil can cause allergic reactions, including hives, itchy palms and possibly nausea and vomiting.

Since flaxseed lowers your blood sugar, when mixed with diabetic medication, your blood sugar may dip alarmingly, so use caution and consult with your doctor. The high levels of fiber may also increase the frequency of your bowel movements so be sure to limit your use of flaxseed in recipes until your body accommodates to high levels of fiber.